(As I think about Karna, my literal mind tries to calculate the age difference between Karna and his brothers. I also want to know, for instance, the average life expectancy of a human at the time of Mahabharata, when is one an adult and when is one considered old? Well I hope I will be able to find answers to these questions as I go along.
In fact, it is now easy to seek information and it is all just a click away on the web! At the same time, we are cautioned that they may not be reliable, they may not be well researched or may be written with a different agenda altogether. Anything and everything can be published on the web! It is as easy for anyone as it is for me!)
Once the education of the princes is complete, Drona exacts his gurudakshina 'I want you to go to the kingdom of Panchalas. I want you to defeat Drupada and bring him to me, a captive. He must not be killed.' Note again the authors comment: 'The hearts of young men will exult at the thought of fighting. This is specially true of khsatriyas.'
'The house of Kuru collected a huge army and marched towards Panchala. .. ..Drupada could not understand the reason for it'. Initially Pandavas keep aloof. 'The Kauravas were defeated. Their army was routed.' The Pandavas step in without Yudhistara and make it straight towards the chariot of Drupada, 'Bheema felling warriors on either side'. Arjuna captures Drupada and speeds towards Drona.
Drona has his revenge as he taunts Drupada. He gives back half the kingdom to Drupada so that they are now equal. And as they are now equal, he hopes that they become friends again. 'Drona, with the short-sightedness typical of a brahmin, thought that it was the end of the matter. He who could nurse an insult for years and devote his entire life to wreak vengeance on the man who insulted him, forgot that a khastriya was capable of a hatred which was just as terrible as that of a brahmin.'
'The anger of a brahmin is short-lived. It is alive just as long as it is not pacified. ... The wrath of a khastriya is more terrible than that of an insulted brahmin. His form burned with anger, with humiliation and hatred for Drona.'
The whole episode ends with an interesting outcome. 'The khastriya in Drupada was full of admiration for the prowess of the young prince Arjuna.' ... as he makes his way back, his mind is on the future '....I will (try to) get two children: a daughter to be given to Arjuna and a son to kill Drona.'